Signaling Connection Control Part (SCCP) provides the Message Transfer Part (MTP) with additional function so that it could transfer circuit-related or non-circuit-related signaling information and other information between exchange offices or between an exchange office and a special center (such as the management and maintenance center) in the telecommunication network via the No. 7 signaling network, and establish connection-oriented and connectionless-oriented services.
In No. 7 signaling network, each signaling point (SP) has a different signaling point code (point code for short). FIG. 1 is an illustration of the No. 7 signaling protocol composition. Wherein, MTP3 denotes the Message Transfer Part layer 3, and SCCP-UP is the SCCP User Part (that is, upper layer protocol).
SIGTRAN (Signaling Transport) protocol is a set of transport control protocols for transporting the PSTN (Public Switched Telephone Network) signaling on IP (Internet Protocol) network. SIGTRAN protocol stack divides into the signaling transport (mainly including IP and SCTP (Stream Control Transmission Protocol)), signaling transport adaptation and signaling application etc. M3UA (MTP3-User Adaptation layer) provides a function for conversion between the signaling point encoding and IP address to transport the No. 7 signaling protocol between the soft switch and the signaling gateway and to support transporting the MTP3 user messages, including ISUP (ISDN User Protocol), TUP (Telephone User Part) and SCCP messages, on the IP network. The M3UA has two work modes: agent and switch.
FIG. 2 is an illustration of the protocol composition of the signaling gateway of the M3UA agent. Wherein, the NIF (Nodal Interworking Function) implements the interworking between the MTP3 and M3UA.
Due to the restriction of the point code resource, the SG (Signaling Gateway) and MGC (Media Gateway Controller) usually have the same signaling point code. For example, in the networking shown in FIG. 3, the SG and MGC are configured with the M3UA protocol and share a signaling point code, and MTP3 link connection is configured between the SG and a plurality of HLRs (Home Location Register) as well as the MSCs (Mobile Services Switching Center). In this networking, the SG has to implement the agent and switch functions.
In the mode of M3UA agent, the SCCP exists in the MGC, and the SG is responsible for transferring the service messages to the SCCP in the MGC. Therefore, the SG is not configured with SCCP user (protocol); otherwise the service messages will terminate at the SCCP in the SG and will not be transferred to the MGC. Which case will certainly result in waste of bandwidth between the SG and the MGC, as well as waste of processing resource of the SG and the MGC. For example, when a message (destination is MSC1) which comes from the HLR and uses GT (Global Title) for routing is transferred through the SG, this message will be sent to the MGC through the M3UA for translation, and the translated message is sent to the SG which will in turn send it to the MSC1 for processing since the SG has no SCCP user. As indicated with 310, 320, 330 and 340 shown in FIG. 3, this message will be transferred back and forth between the SG and the MGC, and the network elements which the message passes are HLR→SG→MGC→SG→MSC1, wasting a lot of bandwidth between the SG and the MGC.
To solve this problem, the SG is assigned with a different signaling point code from the MGC in the prior art so that the SG could be configured with the SCCP protocol to implement the SG switch function. However, this solution needs to add another signaling point code, which is usually not allowed by the operators in the scenarios that the point code resource is short and the 2G devices need to be updated.